A necessity... But how would it be implemented?
A stage for Waluigi does not have to impose significant animation traits. It can simply just have some cool background effects, like pinballs being hit with the flippers; special effects and, of course, the Waluigi Pinball theme; both the remix and original versions.
It would be neat, if there must be some form of hazard, to implement some functional flippers to hit the players whenever they tough them. Like, have the players be in the middle of a pinball game, standing on one of the slopes that is in the middle; and it is big enough to scale down and upwards. Similar to this:
Like, having the flippers function to hit you, being able to go into the water and being eaten by the fish. So, perhaps, using the base from the Ice Climbers stage for the fish...
Wait, now I'm just talking about an idea for a Sonic Spinball stage.
Okay, for the Waluigi Pinball, I was just thinking it could have a similar platform layout, but have the flippers work and being able to knockback the player. Maybe, have a pinball that actually glides around the stage as well that the flippers also hit, and they can sometimes deal deadly knockback damage as well.
It is just a small idea, but it could work as a big stage and it would be pretty fun if some creative effort was given. At the very most, maybe just have it be a fun pinball stage with platforming and, maybe, functional flippers. Otherwise, maybe just something with background animations on a generic stage with three platforms, or no platforms at all so you can see the background action.